Sustainable decision-making through stochastic simulation: Transporting vs. recycling aggregates for Portland cement concrete in underground mining projects

Authored by Marcelo Gonzalez, Ivan Navarrete, Paz Arroyo, Gabriel Azua, Jose Mena, Martin Contreras

Date Published: 2017

DOI: 10.1016/j.jclepro.2017.05.012

Sponsors: No sponsors listed

Platforms: No platforms listed

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

The procurement of high-quality aggregates is a global problem. In Chile, mining companies are in the process of developing massive underground projects that require the extensive use of Portland cement concrete (PCC), approximately 60\%-75\% of which is aggregate. Currently, mining projects transport all the required aggregate to the site from stockpiles that can be more than 100 km away, while mining excavations produce millions of cubic meters of waste rock (WR) that are disposed of in landfills. The use of WR in PCC seems to be a sustainable solution for the production of PCC, but decision-makers lack the tools to support a sustainable decision based on CO2 emissions and operation costs. This paper proposes a methodology that uses stochastic simulation tools to evaluate CO2 emissions and operation costs to decide when it is sustainable to use WR in PCC for underground mining projects. The main objective of this paper is to provide a methodology to quantify CO2 emissions and the cost of transporting natural aggregate versus recycling WR for PCC production in tunneling operations. A sensitivity analysis is also presented, which considers scenarios that include natural aggregate transportation distances of 50, 60, 70, 80, 90, and 100 km, and 0\%, 25\%, 50\%, 75\%, and 100\% replacement of natural aggregate with recycled WR in PCC. The results indicate that the use of WR leads to reductions in CO2 emissions only for natural aggregate transportation distances of greater than 70 km owing to the emissions produced when recycling WR. In addition, 100\% replacement of natural aggregate with recycled WR leads to a greater reduction in CO2 emissions than that obtained in scenarios in which a percentage of the required natural aggregate is obtained from WR. In terms of costs, 100\% replacement of natural aggregate with recycled WR is the most economical alternative for most scenarios; however, the cost reduction varies with the required transportation distance of natural aggregate. It is concluded that using 100\% recycled WR in PCC leads to lower CO2 emissions and costs as compared to the traditional approach in which the natural aggregate is procured from a site located at a distance of 70 km or more from the construction site, under model assumptions. (C) 2017 Elsevier Ltd. All rights reserved.

Tags

agent-based simulation Agent-based modeling Sustainability Portland cement concrete Mining waste rock Co2 emissions Waste-rock